I gave it a 10 because it was the first episode in a long time to make me feel something. It finally had it all.
Let me first express my suprise they killed off two major characters (well, major for the 3rd season). Killing Tracy was an expected thing, but she really went out of the show in one of the most amazing scenes from the start of Heroes. Music, camera movement and the effects were amazing. Touching, even if you hate Tracy/Ali/Niki/Jessica or whoever she is/was. And as for Daphne... the last scene was as amazing as Hiro and his mother's "goodbye" scene. Really sad, really well written. This is why I gave the episode a 10. As for the rest of 'Cold Snap', I have no complaints. Micah was well brought back to the show, Angela had some great scenes, especially the one in the elevator. And Peter was so cool (which can't be said too often) just looking at the SWAT team. His grey coat made quite an impression on me, for reasons unknown.
Hiro and Ando, were just hilarious and not boring at all. The new level of dialogues can really be sensed, and Hiro's powers were long missed by me. I hope they forget the whole 'Save the future' thing and keep Hiro in the present (although I'd like to see the whole show go in the World-splitting-in-half direction).
All in all, a great new direction for all the characters. Mr Fuller better be doing these kind of things again so Heroes can continue where it was left - from being ultimately great.